News
Sunflowers make small moves to maximize their Sun exposure – physicists can model them to predict how they grow
Charles Darwin’s detailed observations of plant movements, such as sunflower circumnutation and self-organization, reveal how randomness helps plants optimize growth and adapt to their environments. Sunflowers!
Chantal Nguyen, University of Colorado Boulder
Most of us aren’t spending our days watching our houseplants grow. We see their signs of life only occasionally – a new leaf unfurled, a stem leaning toward the window.
But in the summer of 1863, Charles Darwin lay ill in bed, with nothing to do but watch his plants so closely that he could detect their small movements to and fro. The tendrils from his cucumber plants swept in circles until they encountered a stick, which they proceeded to twine around.
“I am getting very much amused by my tendrils,” he wrote.
This amusement blossomed into a decadeslong fascination with the little-noticed world of plant movements. He compiled his detailed observations and experiments in a 1880 book called “The Power of Movement in Plants.”
In one study, he traced the motion of a carnation leaf every few hours over the course of three days, revealing an irregular looping, jagged path. The swoops of cucumber tendrils and the zags of carnation leaves are examples of inherent, ubiquitous plant movements called circumnutations – from the Latin circum, meaning circle, and nutare, meaning to nod.
Circumnutations vary in size, regularity and timescale across plant species. But their exact function remains unclear.
I’m a physicist interested in understanding collective behavior in living systems. Like Darwin, I’m captivated by circumnutations, since they may underlie more complex phenomena in groups of plants.
Sunflower patterns
A 2017 study revealed a fascinating observation that got my colleagues and me wondering about the role circumnutations could play in plant growth patterns. In this study, researchers found that sunflowers grown in a dense row naturally formed a near-perfect zigzag pattern, with each plant leaning away from the row in alternating directions.
This pattern allowed the plants to avoid shade from their neighbors and maximize their exposure to sunlight. These sunflowers flourished.
Researchers then planted some plants at the same density but constrained them so that they could grow only upright without leaning. These constrained plants produced less oil than the plants that could lean and get the maximum amount of sun.
While farmers can’t grow their sunflowers quite this close together due to the potential for disease spread, in the future they may be able to use these patterns to come up with new planting strategies.
Self-organization and randomness
This spontaneous pattern formation is a neat example of self-organization in nature. Self-organization refers to when initially disordered systems, such as a jungle of plants or a swarm of bees, achieve order without anything controlling them. Order emerges from the interactions between individual members of the system and their interactions with the environment.
Somewhat counterintuitively, noise – also called randomness – facilitates self-organization. Consider a colony of ants.
Ants secrete pheromones behind them as they crawl toward a food source. Other ants find this food source by following the pheromone trails, and they further reinforce the trail they took by secreting their own pheromones in turn. Over time, the ants converge on the best path to the food, and a single trail prevails.
But if a shorter path were to become possible, the ants would not necessarily find this path just by following the existing trail.
If a few ants were to randomly deviate from the trail, though, they might stumble onto the shorter path and create a new trail. So this randomness injects a spontaneous change into the ants’ system that allows them to explore alternative scenarios.
Eventually, more ants would follow the new trail, and soon the shorter path would prevail. This randomness helps the ants adapt to changes in the environment, as a few ants spontaneously seek out more direct ways to their food source.
In biology, self-organized systems can be found at a range of scales, from the patterns of proteins inside cells to the socially complex colonies of honeybees that collectively build nests and forage for nectar.
Randomness in sunflower self-organization
So, could random, irregular circumnutations underpin the sunflowers’ self-organization?
My colleagues and I set out to explore this question by following the growth of young sunflowers we planted in the lab. Using cameras that imaged the plants every five minutes, we tracked the movement of the plants to see their circumnutatory paths.
We saw some loops and spirals, and lots of jagged movements. These ultimately appeared largely random, much like Darwin’s carnation. But when we placed the plants together in rows, they began to move away from one another, forming the same zigzag configurations that we’d seen in the previous study.
We analyzed the plants’ circumnutations and found that at any given time, the direction of the plant’s motion appeared completely independent of how it was moving about half an hour earlier. If you measured a plant’s motion once every 30 minutes, it would appear to be moving in a completely random way.
We also measured how much the plant’s leaves grew over the course of two weeks. By putting all of these results together, we sketched a picture of how a plant moved and grew on its own. This information allowed us to computationally model a sunflower and simulate how it behaves over the course of its growth.
A sunflower model
We modeled each plant simply as a circular crown on a stem, with the crown expanding according to the growth rate we measured experimentally. The simulated plant moved in a completely random way, taking a “step” every half hour.
We created the model sunflowers with circumnutations of lower or higher intensity by tweaking the step sizes. At one end of the spectrum, sunflowers were much more likely to take tiny steps than big ones, leading to slow, minimal movement on average. At the other end were sunflowers that are equally as likely to take large steps as small steps, resulting in highly irregular movement. The real sunflowers we observed in our experiment were somewhere in the middle.
Plants require light to grow and have evolved the ability to detect shade and alter the direction of their growth in response.
We wanted our model sunflowers to do the same thing. So, we made it so that two plants that get too close to each other’s shade begin to lean away in opposite directions.
Finally, we wanted to see whether we could replicate the zigzag pattern we’d observed with the real sunflowers in our model.
First, we set the model sunflowers to make small circumnutations. Their shade avoidance responses pushed them away from each other, but that wasn’t enough to produce the zigzag – the model plants stayed stuck in a line. In physics, we would call this a “frustrated” system.
Then, we set the plants to make large circumnutations. The plants started moving in random patterns that often brought the plants closer together rather than farther apart. Again, no zigzag pattern like we’d seen in the field.
But when we set the model plants to make moderately large movements, similar to our experimental measurements, the plants could self-organize into a zigzag pattern that gave each sunflower optimal exposure to light.
So, we showed that these random, irregular movements helped the plants explore their surroundings to find desirable arrangements that benefited their growth.
Plants are much more dynamic than people give them credit for. By taking the time to follow them, scientists and farmers can unlock their secrets and use plants’ movement to their advantage.
Chantal Nguyen, Postdoctoral Associate at the BioFrontiers Institute, University of Colorado Boulder
This article is republished from The Conversation under a Creative Commons license. Read the original article.
STM Daily News is a vibrant news blog dedicated to sharing the brighter side of human experiences. Emphasizing positive, uplifting stories, the site focuses on delivering inspiring, informative, and well-researched content. With a commitment to accurate, fair, and responsible journalism, STM Daily News aims to foster a community of readers passionate about positive change and engaged in meaningful conversations. Join the movement and explore stories that celebrate the positive impacts shaping our world.
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News
Untreated sewage and fertilizer runoff threaten the Florida manatee’s main food source, contributing to malnutrition
Aarin-Conrad Allen, Florida International University
The gentle, slow-moving Florida manatee has no natural predators.
And yet, these charismatic mammals face numerous threats.
Manatees are struck by vessels in busy waterways across the state, and a majority bear scars from these collisions.
Harmful algal blooms – characterized by the rapid growth of algae that degrades water quality – can impair their nervous systems.
With less blubber, or fat, compared with other marine mammals like whales, dolphins, seals and sea lions, manatees are vulnerable to cold-stress syndrome during winter months.
And they can ingest or get entangled in marine debris like derelict fishing gear and drown or be crushed by floodgate and water control structures.
I am a doctoral candidate in marine biology at Florida International University’s Institute of Environment. Over the past 15 years, I have gained extensive experience working with marine mammals, particularly manatees.
Recently, my colleagues at the United States Geological Survey, Florida Department of Environmental Protection and I documented a change in the dietary pattern of manatees. We found that manatees are eating less seagrass – traditionally their primary food source – and more algae than in decades past. This change occurred along Florida’s Atlantic coast during a period of extensive seagrass decline.
We believe this represents an emerging threat to the species’ survival.
Protected species
Manatees were listed as an endangered species under the Endangered Species Act of 1973. By the early 1990s, the manatee population in Florida had dwindled to less than 1,300.
Researchers believe that federal protection, along with additional state measures such as slow-speed zones and no-entry refuges, has contributed to the growth of the manatee population in Florida.
In 2017, manatees were reclassified from endangered to threatened. Surveyors counted 5,733 individual manatees during a statewide aerial survey conducted in 2019.
Florida manatees average 9-12 feet (2.7-3.7 meters) in length and typically weigh about 1,000 pounds (450 kilograms), but they can grow as large as 3,500 pounds (1,600 kilograms). As the largest fully aquatic herbivore, they consume 5% to 10% of their body weight in vegetation each day.
While manatees eat a broad diet of over 60 different plants, they most commonly feed on species of seagrass. Seagrasses are marine plants that, like land plants, have leaves, flowers, roots and seeds, and make their food through photosynthesis.
So what happens when these seagrasses are no longer available?
A changing estuary
The Indian River Lagoon is an estuary along Florida’s east coast that covers roughly 350 square miles (560 square kilometers) between the mainland and barrier islands, from Ponce Inlet to Jupiter Inlet.
It is a critical habitat for manatees, which feed on native seagrass meadows in the lagoon during their seasonal migrations.
Seagrasses are vital to the health of marine ecosystems. They are a habitat for juvenile fish and other marine organisms, provide food for aquatic herbivores, reduce carbon in the atmosphere and improve water quality. They also protect coastal habitats by stabilizing sediments and reducing wave energy that can erode shorelines and damage coastal infrastructure, especially during hurricanes.
For more than a decade, the Indian River Lagoon has experienced extensive loss of seagrass meadows, due to a series of algae blooms associated with nutrient runoff and degraded water quality from septic overflow leaching into the environment.
When untreated sewage and fertilizers flow into the estuary, they add nitrogen, phosphorus and other nutrients that drive excessive algal growth. These harmful algal blooms deplete oxygen levels and block sunlight, which seagrass needs for photosynthesis.
Between 2011 and 2019, over 50% of all seagrass in the lagoon was lost. This led to an increase in macroalgae and even led to a change in the animal communities that live in the lagoon. For example, among finfish, sheepshead populations declined, while seabream numbers increased. Invertebrate communities were also affected, with bryozoans colonizing areas previously dominated by barnacles.
Manatees along the Atlantic coast have suffered two unusual mortality events since the seagrass decline, including one that is ongoing. Researchers attribute the increase in manatee deaths to malnutrition due to a shortage of seagrasses in the Indian River Lagoon.
A shift in manatees’ diet
In our study, we examined 193 manatee stomach samples collected from carcasses recovered from the Indian River Lagoon during two time periods – one before and one after the onset of the seagrass loss in 2011.
We compared stomach sample contents from carcasses collected between 1977 and 1989 with samples collected between 2013 and 2015.
Our findings indicate that manatees consumed 45% less seagrass and 74% more algae after the seagrass decline.
Recently, in a study supported by FIU’s Center for Aquatic Chemistry and Environment, I investigated differences in the nutritional composition – like protein, fat, carbohydrate and fiber – of items identified in manatee stomach samples. My preliminary results show notable differences in the nutritional composition of seagrass and algae.
Marine mammals are particularly vulnerable to dietary shifts due to their large size and high energy demands. Such changes can worsen their physical health and increase the likelihood of starvation.
Depleted oxygen levels are having a similar impact on aquatic vegetation and seagrass meadows in other regions of Florida, like Biscayne Bay and the Caloosahatchee River and Estuary. This suggests that the ecological challenges seen in the Indian River Lagoon could become more widespread.
What is the solution?
Remediation efforts within the lagoon have incorporated the restoration of seagrass through aquaculture and replanting strategies, similar to efforts to restore coral reefs.
While the lagoon’s seagrass has recently shown signs of regrowth, the rehabilitation of the ecosystem must begin with improving and maintaining water quality.
Counties along the lagoon have enacted fertilizer bans that aim to reduce the levels of nitrogen and phosphorus in the water that drive algal blooms.
New research, however, indicates that these restrictions alone will not fix the problem, as residential septic systems are the primary source of nutrient pollution in the lagoon.
Furthermore, many of the factors contributing to harmful algal blooms are intensified by global warming and changing climate, which could accelerate the decline of seagrass in Florida and elsewhere.
Given the multiple, synergistic threats facing manatees, I believe that improving water quality, protecting their food sources, and further research – coupled with community outreach and education – are critical to ensure the long-term survival of this iconic Florida species.
Aarin-Conrad Allen, Ph.D. Candidate in Marine Sciences, Florida International University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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College Life
Campus diversity is becoming difficult to measure as students keep their race and ethnicity hidden on college applications
When the Supreme Court struck down race-based admissions at American colleges and universities just over a year ago, many predicted U.S. campuses would become much less diverse. But in part due to students who decide not to disclose their race or ethnicity, coupled with universities’ selective use of statistics, it is not clear how much the decision has affected diversity on campus.
As higher education institutions begin reporting the racial makeup of the class of 2028 – the first to be affected by the 2023 decision – the data is hard to interpret, confusing and inconclusive.
As a sociologist who has studied how institutions of higher education collect and report data on race and ethnicity, I have identified some factors that contribute to this lack of clarity.
Students don’t identify with choices given
Some students may not select a racial or ethnic category because they don’t believe any of the categories really fit. For example, before multiracial students could select “one or more,” an option that became widely available in 2010, they were more likely to decline to identify their race or ethnicity. Some even boycotted checkboxes entirely.
Other students don’t view their race as important: 67% of the students who choose “race and ethnicity unknown” are white. Of these students, 33% say race and ethnicity are not a relevant part of their identity, a researcher found in 2008.
The number of students who don’t respond to questions about race or ethnicity – and are listed in the “race unknown” category – is increasing. At Harvard University, for example, the percentage of “race-unknown” undergrad students doubled from 2023 to 2024.
As the number of “race unknown” students grows, it not only becomes harder to determine a student body’s ethnic and racial diversity but also the impact of the ban on race-conscious admissions.
Fearing discrimination, students don’t disclose race
Some students believe their race or ethnicity will harm their chances of admission.
This is particularly true at many selective institutions, which have higher nonresponse rates than less selective institutions, about 4% compared with 1% to 2%.
My research shows that students are even more likely to pass on identifying race or ethnicity at selective law schools, where race and ethnicity could be used among a variety of criteria for admissions before the Supreme Court ruled against that practice. An average of 8% of students at those schools chose not to identify, compared with 4% at less selective law schools.
‘We’re very diverse’: University decisions distort statistics
What a university chooses to report will also affect the student body demographic data the public sees. Harvard, for example, does not report its proportion of white students.
Some institutions use statistics strategically to appear more diverse than they are. These strategies include counting multiracial students multiple times – once for each race selected – or including international students as a separate category in demographic pie charts. The greater the number of different-colored slices on the chart, the more demographically “diverse” an institution appears to be.
Impact of Supreme Court ruling: Clearer picture coming soon
While universities may not all report their student demographics the same way in their own materials, they all have to report it the same way to the federal government – namely, to its Integrated Post Secondary Education Data System, better known as IPEDS. The next IPEDS report on characteristics for the 2024 enrollment class is expected to be released in spring 2025. Once that data is available, a better picture of how the Supreme Court’s decision has affected diversity in college enrollment should emerge.
That clearer picture might not last long. In 2027, the federal government will require colleges and universities to make changes to how they report student race and ethnicity. Among the changes is the addition of a Middle Eastern and North African category. Under the current standard, Middle Eastern and North African students are counted as white. As a result, white enrollment at some colleges and universities will appear to decline after 2027.
The new standards will also change the way universities treat Hispanic or Latino ethnicity on enrollment forms. Today, if students self-identify as Hispanic and white, they will be categorized as Hispanic. If students select Hispanic and white in 2027, they will be categorized as multiracial. The revised categories will muddy the impact of the Supreme Court’s decision. A drop in the number of Hispanic students reported could be due to the court’s ruling. Or it may result from the new way students will be counted.
Until universities and colleges adjust to the new guidelines about collecting and reporting race – and as long as students decline to provide their racial identities – the full effect of banning consideration of race in college admissions will remain a cloudy picture at best.
Karly Sarita Ford, Associate Professor of Education and Sociology, Penn State
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The Bridge is a section of the STM Daily News Blog meant for diversity, offering real news stories about bona fide community efforts to perpetuate a greater good. The purpose of The Bridge is to connect the divides that separate us, fostering understanding and empathy among different groups. By highlighting positive initiatives and inspirational actions, The Bridge aims to create a sense of unity and shared purpose. This section brings to light stories of individuals and organizations working tirelessly to promote inclusivity, equality, and mutual respect. Through these narratives, readers are encouraged to appreciate the richness of diverse perspectives and to participate actively in building stronger, more cohesive communities.
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Health
10 Simple Changes You Can Make Today for Improved Health and Wellness
Improve your health and wellness with these simple changes to your daily routine.
Boost Your Wellbeing with These Easy Tips
Living a healthy lifestyle is important for our physical and mental well-being, but sometimes it can be overwhelming to know where to start. However, there are simple changes that we can make to our daily routines that can have a big impact on our health and wellness. Here are 10 simple changes you can make today to improve your health and wellness.
- Drink more water: Staying hydrated is key for our body’s systems to function properly. Aim for at least 8 glasses of water a day.
- Add more fruits and vegetables to your diet: Fruits and vegetables are packed with nutrients and antioxidants that can help protect against diseases. Aim for at least 5 servings a day.
- Move more: Regular exercise is important for maintaining a healthy weight, reducing stress, and improving overall health. Find activities that you enjoy and aim for at least 30 minutes of physical activity a day.
- Get enough sleep: Sleep is essential for our body to heal and regenerate. Aim for 7-9 hours of sleep each night.
- Reduce stress: Chronic stress can have negative effects on our physical and mental health. Find activities that help you relax and reduce stress, like meditation or yoga.
- Practice good hygiene: Good hygiene practices like washing your hands regularly and showering daily can help prevent the spread of germs and illnesses.
- Limit alcohol intake: Drinking too much alcohol can have negative effects on our liver and overall health. Limit your intake to no more than 1-2 drinks per day.
- Quit smoking: Smoking is a major cause of many diseases and can have negative effects on our health. Quitting smoking is one of the best things you can do for your health.
- Wear sunscreen: Protect your skin from the harmful effects of the sun by wearing sunscreen with at least SPF 30, especially when spending time outdoors.
- Connect with others: Social connections are important for our mental health and well-being. Make an effort to spend time with friends and family, or find a community group that interests you.
Making these simple changes to your daily routines can have a big impact on your health and wellness. Remember that small steps can lead to big changes. Start with one or two changes and gradually add more as you feel comfortable. With time, these habits will become a natural part of your daily routine, helping you to live a healthier and happier life.
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